This is an ongoing project to provide pregnant monkeys with known dates of pregnancy for various research projects. The time of ovulation is controlled by exogenous progesterone injections (5 mg/day for 10 days). The ovulations are induced by endogenous gonadotropins and occur 16 to 18 days after the last progesterone injection. The species of monkeys used this year are Macaca mulatta, M. fascicularis, and M.nemestrina. The pregnancies are detected by ultrasonography at 38 days after the last progesterone injections in M. mulatta and M. fascicularis and at 45 in M. nemestrina. The pregnancies are confirmed by elevated circulating progesterone determined by RIA. The fetuses are examined by ultrasonography at weekly intervals until parturition. The exams include the measurements of gestation sac, crown-rump length,bipartial diameter, femur length, and heart rate as well as the observation of placental anomalies. The pregnancy rate has been maintained at 60+% for first cycle matings and there have been no problems associated with the weekly examinations of the pregnant females. These examinations have made it possible to detect fetal problems and to deliver infants by cesarean section and to determine if experimental procedures affect fetal development.